Anti-Rattle System Loudspeaker Device ... Anti-Rattle Loudspeaker Panel ANTI-RATTLE SYSTEM...

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Transcript of Anti-Rattle System Loudspeaker Device ... Anti-Rattle Loudspeaker Panel ANTI-RATTLE SYSTEM...

  • Anti-Rattle

    Loudspeaker

    Panel

    ANTI-RATTLE SYSTEM LOUDSPEAKER DEVICE

    Dario Cinanni 1

    , Carlo Sancisi 1

    1ASK Industries Spa, subject to direction and coordination of JVCKENWOOD Corporation via Dell’Industria, 12/14/16 - 60037 Monte San Vito (An) - Italy

    Correspondence should be addressed to author (CinanniD@askgroup.it)

    On the basis of loudspeaker cabinets and panels vibration problems, this study deals with a new dynamic loudspeaker device capable to reduce mechanical vibrations transmitted to the panel where it is fixed. Virtual 3D prototype is designed and optimized by simulations. Simulations were carried out using analytical and finite element methods. A working prototype was realized, measured and then tested on a panel, in order to evaluate vibrations reduction.

    ABSTRACT

    Firstly, a standard woofer was implemented, using a ferrite magnetic assembly, steel basket, rubber surround and a paper cone.

    1. STANDARD LOUDSPEAKER MODEL SETUP

    Loudspeaker 3D design was imported in COMSOL, solved for the magnetic field and structural mechanics physics.

    Figure 1. Standard loudspeaker parts. Figure 2. Loudspeaker electric impedance,

    measurement vs simulation plot comparison. Figure 3. RMS displacement vs frequency and amplitude.

    Figure 4. RMS displacement vs frequency @5V amplitude. Measurement vs

    simulation plot comparison.

    Real loudspeaker prototype moving parts were measured using a laser on membrane center along its axis movement.

    Displacement @5V is used to compare measured and simulated amplitude.

    Figure 5. Transducer magnetic assembly and cut lines displayed

    for flux density analysis.

    Figure 6. Simulated magnetic flux density plotted on the cut line inside transducer gap.

    Figure 7. Simulated magnetic flux density plotted on the cut line on the magnetic assembly external side.

    2. ANTI-RATTLE LOUDSPEAKER SYSTEM DESIGN

    Figure 8. 2DOF TMD.

    Anti-Rattle system doesn’t represent a loss factor for loudspeaker acoustic performances. On the contrary it helps transducer eliminating structure self-vibrations. The first developed prototype reveals about 50% of panel vibrations reduction. But the latest simulations show the way to improve these results.

    Figure 9. Loudspeaker with the Anti-Rattle system. Figure 10. Simulated Von Mises

    Stress on Anti-Rattle springs.

    Figure 13. The new magnetic assembly will create a double magnetic gap, in which the double winding Anti-Rattle

    voice coil will move.

    Figure 12. Simulated magnetic flux density.

    Figure 14. Simulated magnetic flux density inside transducer gap.

    Figure 15. Simulated magnetic flux density inside the Anti-Rattle gaps.

    3. ANTI-RATTLE LOUDSPEAKER SYSTEM RESULTS

    1. J. K. Iverson, The Theory of Loudspeaker Cabinet Resonances, AES 42nd Convention, Los Angeles, California, 1972 May 5.

    2. J. Backman, Effect of Panel Damping on Loudspeaker Enclosure Vibration, AES 101st Convention, Los Angeles, California, 1996 November 8–11.

    3. J. Backman, Computing the Mechanical and Acoustical Resonances in a Loudspeaker Enclosure, AES 102nd Convention, Munich, Germany, 1997 March 22-25.

    4. S. Lipshitz, M. K. Heal, J. Vanderkooy, An Investigation of Sound Radiation by Loudspeaker Cabinets, AES 90th Convention, Paris, France, 1991 February 19-22.

    5. S. W. Stevens, Sound Radiated from loudspeaker Cabinets, AES 50th Convention, London, UK, 1975 March.

    6. O. Døssing, C. Hoffmann, L. Matthiessen, O. J. Veiergang, Measurement of Operating Modes on a Loudspeaker Cabinet, AES 87th Convention, New York, US, 1989 October 18-21.

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    9. K. J. Bastyr, D. E. Capone, On the Acoustic Radiation from a Loudspeaker’s Cabinet, J. Audio Eng. Soc., Vol. 51, No. 4, 2003 April.

    10. M. Cobianchi, M. Rousseau, Predicting the Acoustic Power Radiation from Loudspeaker Cabinets: a Numerically Efficient Approach, AES 139th Convention, New York, US, 2015 October 29 - November 1.

    11. N. Demoli, D. Djurek, Vibrations in the loudspeaker enclosure evaluated by hot wire anemometry and laser interferometry, AES 130th Convention, London, UK, 2011 May 13-16.

    12. M. Nakashima, Y. Hamada, A. Van Gils, I. Bosmans, C. Coster, D. Sacré, Experimental and numerical analysis of loudspeaker induced door rattle, Proceedings of ISMA 2016.

    13. S. R. Hsieh, V. J. Borowski, J. Y. Her, S. W. Shaw, A CAE Methodology for Reducing Rattle in Structural Components, SAE Technical Paper, 1502, 1997.

    14. N. Narayana, A Finite Element Method for Effective Reduction of Speaker-Borne Squeak and Rattle Noise in Automotive Doors, SAE Technical Paper, 1583, 2011.

    15. H. B. J. Nyholm, J. C. Severinsen, H. Schneider, N. H. Mortensen, M. A. E. Andersen, Construction of Lightweight Loudspeaker Enclosures, AES 142nd Convention, Berlin, Germany, 2017 May 20-23.

    16. K. J. Bastyr, C. B. Ickler, R. S. Wakeland, System and Method for Reduced Baffle Vibration, US patent 2009/0257611, 2009 October 15.

    17. K. J. Bastyr, M. W. Stark, System and Method for Reducing Baffle Vibration, US patent 2010/0027816, 2010 February 4.

    18. G. Nichols, M. D. Rosen, H. P. Greenberger, Baffle Vibration Reducing, US patent 7,983,436, 2011 July 19.

    19. M. A. Dodd, Loudspeaker with Force Cancelling Configuration, US patent 9,191,747, 2015 November 17.

    20. S. Tanaka, K. Tamura, S. Kageyama, Bass Speaker, US patent 5,850,460, 1998 December 15.

    21. G. C. Chick, H. P. Greenberger, R. Litovsky, C. B. Ickler, R. Mark, G. Nochols, Passive Acoustic Radiating, US patent 7,133,533, 2006 November 7.

    22. S. Egawa, K. Inanaga, K. Maeda, A. Shimizu, Deleterious Mechanical Vibrations from Dynamic Loudspeaker Offset by Additional Dynamic Device, US patent 4,176,249, 1979 November 27.

    23. T. Hikida, Speaker Balancer, JP patent 2218298, August 08 1990.

    24. M. Servadio, Electro-Magnetic Transducer and Vibration Control System, US patent 2015/0280634, 2015 October 1.

    25. A. Mäkivirta, A. Varla, Method and Arrangement for attenuating Mechanical Resonance in a Loudspeaker, EP patent 0917396, 1998 November 11.

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    27. S. T. Nevill, Decoupled Drive Unit for a Loudspeaker Enclosure, US patent 9,241,206, 2016 January 19.

    28. G. Zhao, B. Zhu, Loudspeaker, CN patent 204031441, 2014 August 07.

    29. F. Cheli, G. Diana, Dinamica e Vibrazione dei Sistemi, Utet Libreria, Reprint 1997.

    30. D. Cinanni, A. Falcioni, C. Sancisi, Altoparlante con Sistema di Controllo delle Vibrazioni, patent pending.

    References

    A loudspeaker with Anti-Rattle structure in a mechanical system can be identified as a TMD (Tuned Mass Damper) with 2-DOF (2 degree of freedom).

    Figure 17. THD comparison of the Anti-Rattle system on/off @4W.

    Figure 18. THD comparison of the Anti-Rattle system on/off @4W.

    The closed box has high mass panels that for a 4W measurement it’s possible to consider the transducer mounted on an infinitely rigid panel.

    Figure 16. Frequency response comparison of the Anti-Rattle system on/off @4W.

    Turning on Anti-Rattle system the THD measurement shows a different behavior in the frequency range 100÷500 Hz.

    Changing Anti-Rattle phase the THD measurement shows a complementary behavior in the same frequency range.

    Eigenfrequencies structure simulation shows the first 4 modes in the range 246÷446 Hz.

    Figure 19. Eigenfrequencies. Fixed constraints on transducer basket screws.

    Figure 22. Simulated panel displacement focused on resonance frequency of the loudspeaker

    excited by a sine sweep. Improved behavior of the Anti-Rattle system given by a phase shift.

    Figure 20, 21. Using a laser scanner vibrometer a structural Frequency Response Function (FRF) comparison of the Anti-Rattle system on/off has been done. Transducer mounted on a wooden

    panel and excited by a filtered Gaussian Noise.

    CONCLUSIONS

    Used tools: Comsol Multiphysics for FEM simulations, Solidworks for 3D design, SpeakerLAB VVC for voice coils calculations, Klippel System for anechoic measurement, Laser Scanner Vibrometer developed by ASK.

    Excerpt from the Proceedings of the 2018 COMSOL Conference in Lausanne